Deleted NameServer, Time to update

I just delete a name server from my registrar. And after that I go back to WHM and try to delete my name server ip. But when I click on the delete function, it keep on displaying the error "CANNOT DELETE NAMESERVER, NAMESERVER STILL REGISTER WITH ICANN SERVER"

Any idea how many hours does it take for the name server to be update? So I am able to delete the nameserver from my server...